The present invention is directed to bicycles and, more particularly, to a bicycle brake control device.
Bicycle brake control devices typically are attached to the handlebar of the bicycle. A conventional brake control device comprises a mounting bracket and a lever, wherein the mounting bracket is mounted on the handlebar, and the lever is pivotably mounted to the mounting bracket. With the exception of reverse levers, brake levers are structured in such a way that the tips point away from the handlebar, regardless of the shape of the handlebar. The lever is connected to a brake device by a brake wire, wherein a return spring that forms a part of the brake device pulls the brake wire in a direction toward the brake device. This causes the lever to rotate toward an initial, nonoperating position. The rider operates the brake by placing the fingers on the lever and by moving the tip of the lever from the initial, nonoperating position toward the handlebar. Braking is released by allowing the lever to return to its initial position.
In conventional brake control devices, the initial position of the lever is determined by the structure of the brake lever and the mounting bracket, and it is usually set to accommodate the average hand size. As a result, the tip of the lever sometimes can be too far away from the handlebar for people with smaller hands to comfortably reach. Also, since the distance from the lever pivot axis at which the fingers grip the lever determines torque applied to the brake wire, the brake device can be operated efficiently with light finger force when the fingers grip near the tip of the lever. However, if it is difficult for the rider's hand to reach the tip of the lever, then the rider is forced to grip the lever closer to the pivot axis. This makes it necessary to apply significantly more force to apply the brakes effectively.
To alleviate such problems, devices have been developed that allow the initial position of the brake lever to be adjusted closer to the handlebar. See, for example, Shimano 2003 Bicycle Components Trade Sales & Support Manual, page 129. Such adjusting devices typically are placed between the mounting bracket and the lever to form a gap between them, thereby setting the initial position of the lever closer to the handlebar.
It is also known to construct brake control devices such that the lever ratio changes as the lever is rotated from the initial position toward a brake operating position. Such a brake control device is disclosed in Japanese Patent Number 3,053,835. The device is formed in such a way that the lever ratio initially causes the brake wire to be pulled at a faster rate during initial rotation of the brake lever until the brake pad of the brake device contacts the wheel rim. Thereafter, the lever ratio is modified to cause a powerful braking force to be applied to the wheel rim with minimum effort by the rider. The brake control device disclosed in the foregoing reference comprises a cam attached to the mounting bracket and a guiding groove formed on the lever. A nipple support used to support a cable end nipple attached to the end of the brake cable is supported by the guiding groove. The cam presses the nipple support toward the pivot axis of the brake lever as the brake lever rotates from the initial position toward the brake operating position, thereby changing the lever ratio as the brake control device operates. Furthermore, the guiding groove is formed in such a way that one end is open and the other end forms a groove floor. The groove floor is located closer to the pivot axis than the open end, and the groove floor is located forwardly of the open end when the lever is in the initial position. The contour of the cam controls the lever ratio until the lever has rotated to a certain position, typically when the groove floor is located directly below the open end. Thereafter, the nipple support slides in the guiding groove toward the pivot axis until the nipple support rests against the groove floor. At that time the rate of pulling of the brake wire decreases with a corresponding increase in mechanical advantage, thus ensuring strong braking force with minimum effort by the rider.
When a conventional adjusting device is used to change the initial position of a lever so that the tip of the lever is closer to the handlebar, wherein the brake control device is of the kind that varies the lever ratio during operation, the nipple support may be pressed by the cam toward the pivot axis in the new initial position. As a result, the lever pulls the brake wire at a reduced rate right from the start, and there may be insufficient total wire stroke to properly operate the brake device.